Method for the production of phthalic and toluic acids by the catalytic oxidation of xylenes

ABSTRACT

Method for the production of phthalic and toluic acids by the catalytic oxidation of a xylene or a mixture of the xylene isomers utilizing air or gas containing molecular oxygen as the primary oxidation agent in conjunction with an isobutane oxidate as a secondary agent. A cobalt salt is the preferred catalyst; however, the salts of metals having atomic numbers 23 - 29 inclusive, can be utilized. The oxidation is carried out at temperatures in the range of from about 220*F. to 320*F., at pressures ranging from 100 to 1,000 psig.

United States Patent [191 Grane Aug. 27, 1974 [54] METHOD FOR THEPRODUCTION OF 3,507,912 4/1970 Behun et al 260/524 R PHTHALIC AND TOLUICACIDS B THE 3,732,314 5/1973 Massie 260/524 R CATALYTIC OXIDATION OFXYLENES [75] Inventor: Henry R. Grane, Springfield, Pa.

[73] Assignee: Atlantic Richfield Company,

Philadelphia, Pa.

[22] Filed: Dec. 18, 1972 [21] Appl. No.: 316,186

[52] US. Cl 260/524 R [51] Int. CL. C07c 51/20, C07c 63/26, C07C 63/02[58] Field of Search 262/524 R [56] References Cited UNITED STATESPATENTS 2,245,528 6/l94l Loder 260/524 R 3,452,087 6/1969 Patton ct al260/524 R Primary Examinerllorraine A. Weinberger AssistantExaminerRichard D. Kelly Attorney, Agent, or Firm-Delbert E. McCaslinABSTRACT Method for the production of phthalic and toluic acids by thecatalytic oxidation of a xylene or a mixture of the xylene isomersutilizing air or gas containing molecular oxygen as the primaryoxidation agent in conjunction with an isobutane oxidate as a secondaryagent. A cobalt salt is the preferred catalyst; however, the salts ofmetals having atomic numbers 23 29 inclusive, can be utilized. Theoxidation is carried out at temperatures in the range of from about2201?. to 320F., at pressures ranging from 100 to 1,000 psig.

8 Claims, N0 Drawings AND TOLUIC ACIDS BY THE CATALYTIC OXIDATION OFXYLENES I V ACKG O ND OF THE INVENTION 1 Processes for producing monoanddicarboxylic aromatic acids by the use of air oxidation are well-known,in particular processes-for producing terphthalic acid and isophthalicacid and the corresponding toluic acids known processes aldehydes orketones are employed as promoters. All of these processes suffer from acorn DiE'scR Pr'io OF -THiE INVENTION This invention-is applicable tothe oxidation of orthometaor para-xylene or inixtures of two or, more ofthese isomers. The products are the; corresponding phthalic acids andtoluic acids? The oxidation is'preferably carried out by bringing amixture of the xylene or xylenes with the catalyst to the desiredreaction tem v 3 perature and then introducing a molecular oxygen gas, IA are known utilizing acetic acid as "a solvent. ln'other preferably airinto the reaction mixture. The air flow is? similar processes bromine isemployed as a promoter i maintained at a rate to hold about 7 weight percent oxtogether with the acetic acid as the solvent and in other 71y'genin the off-gas when a pressure of about 500 psig I V v is employed.Reaction temperatures of from 220 F. to

mon disadvantage, namely, they are highly corrosive I and requirethe useof expensive alloys in the reactor The present invention avoids the useof corrosive solvents or promotersand is amenable to semi-L continuousor continuous operation.

SUMMARY OF THE INVENTION In accordance with the process of thisinvention a single xylene isomer or a mixture of two or more of theisomers is reacted with air or molecular oxygen in the presence of anoxidate produced by the oxidation of isobutane with molecular oxygen andin the presence of a metal salt as the catalyst wherein the metal isselected from those of atomic numbers 23 29 inclusive of the PeriodicTable, preferably however, a cobaltcatalyst. The xylene or xylenestogether with the metal catalyst are charged to a reactor and afterpurging with an inert gas such as nitrogen, the contents are-heated tothe reaction temperature and air flow started under the desiredpressure. The isobutane oxidate from which the unreacted isobutane wasstripped is then introduced into the reactor and the air or oxygen flowcontinued until the desired conversion has been attained. High yields ofphthalic and toluic acids are achieved by this method. The isobutaneoxidate which is composed primarily of a mixture of tertiary butylhydroperoxide and tertiary butyl alcohol is generally substantially.

320 FL can be employed with temperatures ranging. f.

frorn 2fi09 F. to 300 F. being preferred and with t ernperatures of'from 270F. to. 29031 .being most? preferred. Pressures of from 100 tol- ,0 00 can be used with 400 to 600 psig being preferred and about 500psig being convenient. 4 i

' The isobutane oxidate isthen terfere with the-reaetioni iTheproduction of the isobutane oxidate.suitable' foruse'injthis reaction isfully described in the US. Pat; Nos-2,845,461 (1958) and The xyleneoxidation is carried-outfor a time ranging from 0:25 to 10.0 hours. Thecatalysts suitable for use in the invention are those having atomicnumbers of from 23 to29 inclusive, i.eL, vanadium chromium, manganese',iron, coba lt, nickel and copper, with cobalt being preferred. The Saltsmay be either organic or in-' organic, such as the *naphthenates, acetylacetonates,-

halides, sulfates and. the like, with the soluble organic air and anisobutane oxidate in the presence of a metal I salts being preferred.The quantity of catalyst can range from 20 parts per million by weightof the metal based on the weight of the xylenes and the oxidate rangingup to 10,000 parts per million by weight of the metal, or

the solubility limit of the catalyst. It is preferred that the oxygencontent be maintained below about 10* weight per cent based on theweight of the reactants in order to stay outside the explosiverange. Nosolvent is I required other thanthe aforementioned isobutane diddatewhich contains an appreciable quantity of tertiary butyl alcohol. v 1

In order to illustrate the invention in' greater detail the followingExample is provided.

introduced into the re: I I

.actor system along with the. air flow while maintaining" y theaforementioned temperatures; pressuresand oxygen content in the off-gasfrom thefireac'ton 4 The isobutane oxidate is preferably prepared bythel'f continuous non-catalytic oxidation "of isobutane withfif air oroxygen at temperatures in the range of.2O0F..-'to f 300F. and pressuresfrom 200 to 1 ,000 psig with times ranging froml .to 20. hour sllt ispreferred to strip the. isobutane oxidate with tertiary. butanoltoremove the unreacted isobutanegThe oxidate is then composedpri- 'marily,i.e., generally. about weight percent of a"; mixture-of teriary butyl'hydroperoxide and tertiary butyl alcohol with the tertiary butylhydroperoxide preferably. in molar excess over the alcohol, depending.upon the conditions employed in oxidationyThe 5 per cent'by productsare also oxygenated'products and are i f J primarily smallaniounts'; i.eof the order of l per cent or less 'of watenmethy-l alcohol; acetone,esters and the like,'These are;irifsuch smallamounts it is unnecessaryto remove them from the oxidate-since they do not in v I EXAMPLE To a 1liter autoclave were added 69 grams of metafxyle neand sufficient cobaltacetyl acetonate to give 185 ppm by weight cobalt in the, mixture. Theauto clavewas itroge'n purged and heated to 280F. Air flow wa s th enstarted to the reactorat a rate sufficient to hold about ;7 weight percent oxygen in the off-gas. with a pressure of 500 psig. Overa 1 hourperiod 420 I i grams of isobutane oxidate was charged to thereactorwhile maintaining the temperature at 280F., the, pres:

had been converted lsophthalic acid amountedto weight per cent of theconverted xylene and metatoluic acid amounted to 76 weight per cent ofthe con verted xylene in the reaction productQThese results show that ahigh conversion and high selectivity can be obtained by the process ofthis invention.

The isobutane oxidate utilized in thislixan'iple prepuredby thecontinuous non-catalytic oxidationby;

isobutane with air at 272F., 435 psig with an average residence time of6 hours. The oxygen in theoff-gas was held at lessthan 5 percent byweighL fThe'oxidate the above described Example.

-lclaim:

l. A process for producing phthalic and toluic acids 1 5. The methodaccording to claim from the group consisting of ortho-, meta-, andparaxylene and mixtures thereof at a temperature in they range of from220F." to 320F. with a molecular oxygen-containing gasunder pressuresranging from v100 to 1,000 psig solelyin the presence of a metal saltcatalyst J andan oxidate produced by the thermal oxidation of isobutanewith molecular oxygen, said oxidate compris ing primarily a mixture oftertiary butyl hydroperoxide' and tertiary butyl alcohol, the metal ofthe said catalyst being selected from the group consisting of vanadium,L} I chromium, manganese, iron, copper, nickel and cobalt.

' 2. The method according to claim 1, wherein the cat- "al'yst is a'cobalt catalyst.

3. The. niethodaccording to claim 2, wherein the hydrocarbonis'meta-xylene and there is produced isoph'thalic acid and meta-toluicacid.

4.,"I 'he .lmethod according to claim 2, wherein the hyd'rocarbonispara-xylene and there is produced terphthalie acid and-paratoluic'acid.

1, wherein the ,tempera'tureis in the range of from 240F. to 300F.

' andthe pressure is in the range of 400 to 600 psig.

. was stripped with tertiary butanoi to remove the unre- 3 actedisobutane and the stripped oxidate was used in.

which comprises contacting a hydrocarbon s elected 6. The methodaccording to claim 5, wherein the catalyst is cobalt acetyl acetonate. I7. The method according to claim 1, wherein the hydrocarbon is contactedwith air as the molecular oxygen-containing gas-the temperature is inthe range of from 270F. to 29 O F., thepressure is about 500 psig, the"oxidate comprisesprimarily about 95 weight per cent of a mixture oftertiary butyl hydroperoxide and I tertiary'butyl alcohol, and thecatalyst is cobalt acetyl acetonate. g

8. The method according to claim 7, wherein the the [hydrocarbonismeta-xylene, and there is produced a mixture of isophthalic acid andmeta-toluic acid.

2. The method according to claim 1, wherein the catalyst is a cobaltcatalyst.
 3. The method according to claim 2, wherein the hydrocarbon ismeta-xylene and there is produced isophthalic acid and meta-toluic acid.4. The method according to claim 2, wherein the hydrocarbon ispara-xylene and there is produced terphthalic acid and paratoluic acid.5. The method according to claim 1, wherein the temperature is in therange of from 240*F. to 300*F. and the pressure is in the range of 400to 600 psig.
 6. The method according to claim 5, wherein the catalyst iscobalt acetyl acetonate.
 7. The method according to claim 1, wherein thehydrocarbon is contacted with air as the molecular oxygen-containinggas, the temperature is in the range of from 270*F. to 290*F., thepressure is about 500 psig, the oxidate comprises primarily about 95weight per cent of a mixture of tertiary butyl hydroperoxide andtertiary butyl alcohol, and the catalyst is cobalt acetyl acetonate. 8.The method according to claim 7, wherein the the hydrocarbon ismeta-xylene, and there is produced a mixture of isophthalic acid andmeta-toluic acid.